How does Hot Dip Galvanizing compare to paint and powder coat?
The Zn (Zinc metal) in HDG (Hot Dip Galvanized) adheres to the steel that it protects with intermetallic bonding which is an order of magnitude stronger than the metal to paint or powder coat bond. The thickness of the Zn coat is determined by the characteristics of the steel and the galvanizing process and is much thicker than electro-galvanized or electro-plated materials. Zn coatings on bulk galvanized materials is generally controlled at the factory to be thinner than HDG Zn films. The strong bonding and the elasticity of the HDG metal film helps ensure no cracks or separation occur as the metal is flexed or expands with temperature. HDG film thickness is almost unchanged with long term exposure to the atmosphere while paint films deteriorate due to oxidation and erosion. Paint and powder coat finishes tend to be thinner at corners and especially at sharp edges and these sites (and scratches and chips) are the places where the film fails and corrosion (rust) forms first. Rust forms
